1. Field of the Invention
This invention is in the field of internal combustion engines and gasifiers and particularly the field of internal combustion engines and gasifiers burning solid fuels alone or in combination with liquid or gaseous fuels. The internal combustion engines can be of the piston and cylinder type or equivalent.
2. Description of the Prior Art
Prior art examples of char burning engines of the piston and cylinder type are described in the following U.S. Patents issued to applicant:
In these example cyclic char burning engines and gasifiers air, or other reactant gas containing appreciable oxygen gas, is compressed into the pore spaces of a solid char fuel, contained within a separate primary reaction chamber, during a compression process and this is followed by expansion of the primary reacted gases, formed by reaction of oxygen with the char fuel, out of the pore spaces of the char fuel during an expansion process. This cycle of compression followed by expansion is repeated. This cycle of compression and expansion is created by a combined means for compressing and expanding, such as a piston operated within a cylinder, wherein the space enclosed by the piston crown and the cylinder walls is a variable volume chamber whose volume varies cyclically when the piston is reciprocated by an internal combustion engine mechanism for driving this combined means for compressing and expanding. Following each expansion process the reacted gases are largely removed from the variable volume chamber by an exhaust means. Fresh air is next supplied into the variable volume chamber by an intake means prior to the next following compression process. Thus an exhaust process followed by an intake process is interposed between each expansion process and the next compression process for a cyclic char burning engine or gasifier as is well known in the art of internal combustion engines. Each compression process occupies a compression time interval which is followed by an expansion process occupying an expansion time interval. The separate primary reaction chamber is contained within a pressure vessel container. A means for preheating the char fuel within the primary reaction chamber is used to bring the char fuel up to that temperature at which it will react rapidly with oxygen in adjacent compressed gases while the engine or gasifier is being started. Thereafter the means for preheating the char fuel can be turned off when the heat of the primary reaction becomes sufficient to keep the char fuel at or above this rapid reaction temperature. During starting a cranking means is used to drive the internal combustion engine mechanism. The detailed descriptions of cyclic char burning engines and gasifiers contained in the above listed U.S. Patents are incorporated herein by reference thereto.
The term char fuel is used herein and in the claims to include highly carbonaceous and largely solid fuels such as coal, coke, charcoal, petroleum coke, etc.
As char fuel is reacted to ashes within the primary reactor it is replaced by a refuel mechanism means for supplying fresh char fuel into a refuel end of the primary reactor. The char fuel is thus moved along through the primary reactor toward an opposite ash collection end of the primary reactor. Hence the char fuel being reacted within the primary reactor has a direction of motion from the refuel end toward the ash collection end. An ash removal mechanism is used as a means for removing ashes from the primary reaction chamber.
Where air is the reactant gas it is readily available from the atmosphere. In some applications oxygen enriched air or essentially pure oxygen may be used as the reactant gas, as for example in some gasifier uses, and here a source of oxygen rich gas is needed.
The term rapid reaction temperature is used herein and in the claims to mean that temperature of the char fuel at which it will react with the supplied reactant gas containing oxygen gas sufficiently rapidly to maintain the char fuel temperature at or above this rapid reaction temperature due only to the heat of the reaction between the char fuel and this reactant gas. This rapid reaction temperature varies with the kind of char fuel being reacted, the oxygen content of the reactant gas, and the operating conditions prevailing within the char fuel reaction chamber.
For the same reactant gas and operating conditions different char fuels have different rapid reaction temperatures, some charcoals reacting rapidly with air in usual type reactors at temperatures as low as 1200.degree. F. whereas some petroleum coke fuels will only react rapidly with air at temperatures above about 1500.degree. F.
For a particular char fuel and operating condition a higher rapid reaction temperature is required when the oxygen content of the reactant gas is reduced since more of the heat of char and oxygen reaction is diverted to the heating up of non reactive portions of the reactant gas. Below a certain minimum oxygen content the reaction between the char fuel and the oxygen is too slow to sustain itself by its own heat of reaction, and the term appreciable oxygen gas content of reactant is used herein and in the claims to mean an oxygen content greater than this minimum value. Ordinary air, with an oxygen gas content of about 21 volume percent, will usually react readily with most commonly available hot char fuels in reasonably well insulated reaction chambers, and is an example of a reactant gas containing appreciable oxygen gas suitable for use in most gas producers. In some gas producer applications oxygen enriched air or essentially pure oxygen has been used as the reactant gas containing appreciable oxygen gas. Reactant gases containing less oxygen than air, while theoretically useable in gas producers, have rarely, if ever, been so used.
As the char fuel reaction chamber becomes smaller, external heat loss rate increases, and the char fuel must be brought to a higher temperature, and thus higher reaction speed, in order for the char fuel and oxygen gas reaction to be self sustaining. We thus see that the rapid reaction temperature is not a property of the char fuel alone and can only be determined experimentally within the reaction chamber to be used, and with the oxygen containing reactant gas to be used.
In some engine applications of cyclic char burning engines and gasifiers, the variable volume chamber of the internal combustion engine may also be used as a secondary reaction chamber wherein primary reacted gases from the primary reactor are burned completely with secondary air during the expansion process. For these applications the needed secondary air is retained outside the primary reactor during compression and is admixed with the primary reacted gas emerging from the primary reactor during expansion. The resulting air fuel mixture is then ignited by an igniter means within the secondary reactor in the variable volume chamber. Thus this form of cyclic char burning engine requires use of a suitable igniter means within the variable volume chamber. In some gasifier uses of cyclic char burning engines and gasifiers secondary air is not thusly retained outside the primary reactor and the variable volume chamber is not also used as a secondary reaction chamber. For both such engine uses and such gasifier uses net work output can be done on the piston, since the various reactions of char fuel with oxygen and of product gases with oxygen are exothermic reactions which are carried out under the varying pressures of the engine cycle. Herein and in the claims the term power reactor is used to mean either a cyclic char burning engine or a cyclic char burning gasifier.
The term fixed open gas flow connection is used herein and in the claims to mean a gas flow passage which remains open whenever the cyclic char burning engine or gasifier is operating.
The term changeable gas flow connection is used herein and in the claims to mean a gas flow passage which can be opened or closed while the cyclic char burning engine or gasifier is operating. A changeable gas flow connection is opened and closed by a drive means for opening and closing and this is driven in turn from the internal combustion engine mechanism drive means as is well known in the art of internal combustion engines.
As the char fuel, within the primary reactor, moves along the char fuel motion direction it is preheated by heat transfer from char fuel portions which are further along and are reacting rapidly with oxygen and thus are at a high temperature. Where the char fuel being used is essentially free of volatile matter, as with coke fuel, this preheat zone serves to bring the new char fuel up to its rapid reaction temperature. The char fuel then enters the rapid reaction zone and carbon reacts therein with oxygen to form producer gas. Beyond the rapid reaction zone in the direction of char fuel motion the char fuel is essentially completely reacted to ashes which pass into an ash collection zone at the end of the char fuel motion path.
In prior art cyclic char burning engines and gasifiers the ashes are removed from the ash collection zone of the primary reactor at the end of the char fuel motion path by an ash removal mechanism. Most such ash removal mechanisms remove a volume of material at intervals and it is necessary to control either the volume, or the interval, or both, so that only ashes, and no unburned char fuel, are removed.
Within the space occupied by the chunks of char fuel within the primary reactor two types of spaces exist. Within each char fuel chunk interior pore spaces exist in most char fuels. Between the char fuel chunks interstitial spaces exist.